Tankless water heater for closed loop shop floor

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Toddjb

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All, I set up this closed loop system for my shop last year. I have 4 closed loops for a total of 1200' of 1/2" pex that is heating 1200sqft split between two main rooms.

PXL_20211011_034959899.jpg


It cost me around $350-400 during the coldest months. That is not what I was expecting based on previous research.

So I'm looking to move to an electric tankless setup. I'm struggling to find good info on how to size a heater for closed loop electric systems.

It seems I get about a 10 degree drop from outlet to inlet.

I would greatly appreciate any info, or even specific recommendations - as I know some units aren't designed to suit the kind of system well.
 

Dustbunny

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I am not a plumber but I think that a BTU is a BTU and a different way to heat the water is going to use the same amount of electricity.

You might gain a small savings by using a tempering valve so some of the return water went right back out again but still... a BTU is a BTU
 

John Gayewski

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An electric tankless? Do you have a large electrical service that you can run a large wire to?

Your building losses heat at whatever rate it's built at. No matter what you use to heat it, it will lose heat at that rate. If you want to save money you want to slow the heat loss, or change to a cheaper fuel. Which means foam and insulation,or gas if it's cheaper.
 

Fitter30

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Electric is 100% efficient 3.3 btu's per watt doesn't matter how its heated by resistance elements its all the same and voltage of element doesn't change anything. What water temps are you running in and out of the heater with full load?
 

Bannerman

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If gas is not an option, you may want to investigate the potential of a heat pump type of water heater.

A heat pump operates similarly to a refrigerator or air conditioner, in which it utilizes electricity to move heat from one location to another. Since it will extract the heat from the surrounding air to heat water, the air source should be from outside of the space that is to be heated.

Perhaps building an insulated enclosure around the heat pump water heater and installing venting to the exterior of the building, may supply sufficient air to provide a sufficient source of heat.
 

Reach4

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Have you considered insulating your shop?
 

Toddjb

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If gas is not an option, you may want to investigate the potential of a heat pump type of water heater.

A heat pump operates similarly to a refrigerator or air conditioner, in which it utilizes electricity to move heat from one location to another. Since it will extract the heat from the surrounding air to heat water, the air source should be from outside of the space that is to be heated.

Perhaps building an insulated enclosure around the heat pump water heater and installing venting to the exterior of the building, may supply sufficient air to provide a sufficient source of heat.

Interesting idea. The current set up is in an uninsulated, unheated part of the building. The two insulated/heated sections are separated. The piping from this unit to where it enters the concrete pads is insulated.
 

Toddjb

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What water temps are you running in and out of the heater with full load?
It's set to 110 for the out. And when the water heater has time to fully recover, when the pump turns off, it will get to 110, but once it's been running a bit, the output is only around 80-85..
 

Fitter30

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It's set to 110 for the out. And when the water heater has time to fully recover, when the pump turns off, it will get to 110, but once it's been running a bit, the output is only around 80-85..
what the in and out temps to see if the flow through the system is correct. Looking for 20°. What is the % of glycol and what type are you using? Also don't see any air eleminator devise.
 

John Gayewski

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Understood, i just assumed my issues was having to keep 60 gallons of water/glycol heated from the tank and tubes, instead of just the 10-ish gallons in the tubes.
This doesn't change your heat loss or effeciancy. Every bit of heat you generate is in your building isn't it? If so your losing nothing to the building but rather the building is losing heat to the outdoors.

Is the slab insulated on the edge and under it? The entire perimeter?
 

Toddjb

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This doesn't change your heat loss or effeciancy. Every bit of heat you generate is in your building isn't it? If so your losing nothing to the building but rather the building is losing heat to the outdoors.

Is the slab insulated on the edge and under it? The entire perimeter?
Yes, the slab is insulated with the recommended foam board under and up the sides.
 

Fitter30

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Just Google your heater looks like it's 4500 watts= 14,850 btu's. Has two elements 4500 each but it only turns on one or the other not both. Water temp drops after a call for heat because the heater doesn't have enough btu's to keep up. Example have a torch to heat something red hot but it never gets it hot enough can keep that torch going forever but won't get it hot where a larger torch would get it hot in minutes. Heater you have only after running a very long time. If you have to panel capacity where heater can run both element at the same time doubling the output.
Screenshot_2022-08-02-10-35-10.png
 

Toddjb

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what the in and out temps to see if the flow through the system is correct. Looking for 20°. What is the % of glycol and what type are you using? Also don't see any air eleminator devise.

Just Google your heater looks like it's 4500 watts= 14,850 btu's. Has two elements 4500 each but it only turns on one or the other not both. Water temp drops after a call for heat because the heater doesn't have enough btu's to keep up. Example have a torch to heat something red hot but it never gets it hot enough can keep that torch going forever but won't get it hot where a larger torch would get it hot in minutes. Heater you have only after running a very long time. If you have to panel capacity where heater can run both element at the same time doubling the output.
View attachment 85390

Sorry, I had a little trouble following that. Your saying that my water heater element will only fire one or the other at a time they way it's currently wired, but it can be wired so that both will fire? Is that a screen shot of how I should wire it?

What amperage is recommended for that?
 

WorthFlorida

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The heating elements are only use one at a time. When cold the upper element is on. When the set temperature of the upper element is satisfied, it switches power to the lower element. The thermostat for the lower element is different. It only switches the power to the element.

The picture above shows how to wire so both elements are used at the same time. The lower thermostat is replaced of the same type as the upper thermostat. Each work independently. The diagram show number six wire feeding the water heater. If you go this route you need to fish wire from the upper thermostat to the to small juncture box to connect to the wires going to the lower element. You'll need to add a juncture box at the top connector since there will not be enough room with #6 wire. You need to increase the breaker to 50 amp.

Another solution is changed the heating elements to a 5500 watt rating. They are sold in hardware stores and alike. This requires no wiring upgrades.

Any increase in wattage will increase your electric bill. If you need more heat, installing a split mini heat pump that can blow warm air into the space Is affordable and quite efficient. Since your building is losing heat, other than adding insulation, it will always cost more to raise the temperature.

Since you are in NC, does the shop have central air? If yes change the compressor unit to a heat pump.
 

Toddjb

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The heating elements are only use one at a time. When cold the upper element is on. When the set temperature of the upper element is satisfied, it switches power to the lower element. The thermostat for the lower element is different. It only switches the power to the element.

The picture above shows how to wire so both elements are used at the same time. The lower thermostat is replaced of the same type as the upper thermostat. Each work independently. The diagram show number six wire feeding the water heater. If you go this route you need to fish wire from the upper thermostat to the to small juncture box to connect to the wires going to the lower element. You'll need to add a juncture box at the top connector since there will not be enough room with #6 wire. You need to increase the breaker to 50 amp.

Another solution is changed the heating elements to a 5500 watt rating. They are sold in hardware stores and alike. This requires no wiring upgrades.

Any increase in wattage will increase your electric bill. If you need more heat, installing a split mini heat pump that can blow warm air into the space Is affordable and quite efficient. Since your building is losing heat, other than adding insulation, it will always cost more to raise the temperature.

Since you are in NC, does the shop have central air? If yes change the compressor unit to a heat pump.
Thanks! No AC unfortunately. I'm in the mountains of Western NC, so it's a bit of reprieve from the low lander heat, but that also means 30 degrees is a fairly common winter day, with quite a few days getting into the teens. 5500 element might be my first line of attack.

Follow up: would there be any issue with running a second 30 amp/10ga wire to the bottom element, instead of going with the 50amp/6ga? I just have all that material on hand.

.
 
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Fitter30

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Thanks! No AC unfortunately. I'm in the mountains of Western NC, so it's a bit of reprieve from the low lander heat, but that also means 30 degrees is a fairly common winter day, with quite a few days getting into the teens. 5500 element might be my first line of attack.

Follow up: would there be any issue with running a second 30 amp/10ga wire to the bottom element, instead of going with the 50amp/6ga? I just have all that material on hand.

.
Yes a second circuit can be run instead of the 50 amp. Still have to replace the lower control. Mark water heater with breaker numbers and note powered by both.
 
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